Policers are a commonly used capability in network infrastructures to measure the flow of frames (Layer 2 or L2) or packets (Layer 3 or L3) from a source to a destination and to subsequently take remedial action if the measurements are above a pre-determined threshold. Remedial actions include dropping packets, re-marking to a different priority (e.g., remarking Differentiated Services Code Point (DSCP) from AF41 to AF42) or doing nothing. There are several reasons why network engineers and network administrators use policers. For example, policers provide for the ability to charge for services based on the data rate allowed to a particular subscriber or class of subscribers. Some wired networks employ a shared medium (e.g., Ethernet hub). In this case, usage by one user of the shared medium takes away resources available to other users—thus, policers are used to enforce a maximum data rate usage for each user so that there are no bandwidth “hogs.” Additionally, many networks provide Quality of Server (QoS) and access to QoS services needs to be limited so as not to overly deprive resources from best-effort services. This is particularly important on bottleneck connections such as wireless or WAN (e.g., T1 trunk) connections.
Currently, policer implementations are uni-directional in nature. Typically, they are instantiated on wired networks whose underlying medium is full duplex (e.g., fiber optic communications where there is a fiber in each direction of transmission between two nodes). In this case, usage of the medium in each direction is independent-usage in one direction does nothing which impacts the available resource in the opposite direction. However, many wireless communication bands are inherently half-duplex in nature. This can occur whenever a contiguous portion of radio spectrum is used for communication between two nodes in both directions. Examples of half-duplex bands include most unlicensed spectrum (e.g., 2.4-GHz ISM, 5-GHz UNII/ISM, 1910-1930 MHz unlicensed PCS). It also includes some licensed spectrum (4.9-GHz, 3.75-GHz, MMDS, PTT bands, etc.). In these bands, usage of the spectrum for one direction of communication prevents simultaneous usage in the opposite direction. Another characteristic of wireless communications is that, generally, a plurality of users are sharing the same spectrum. This means that usage by one user negatively impacts the amount of capacity available to other users in a wireless network.